Performance Analysis of Multilayer MIPv6 Architecture through Experimental Testbed

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1 1682 JOURNAL OF NETWORKS, VOL. 9, NO. 7, JULY 214 Performance Analysis of Multilayer MIPv6 Architecture through Experimental Testbed Nitul Dutta MEF Group of Institutions, Computer Engg. Department, Rajkot, Gujarat, India Iti Saha Misra Jadavpur Univesity, ETCE Department, Kolkata,West Bangal, India Kushal Pokhrel and Mrinal K Ghose Sikkim Manipal Instute of Tech, Computer Engg. Department, Majitar, Sikkkim, India itisahamisra@yahoo.co.in Abstract Mobility management is a key issue to achieve uninterrupted Internet services in IP based network. In IPv6, the mobility management is realized by its mobile version namely the Mobile IPv6 (MIPv6). The MIPv6 is further extended to Hierarchical MIPv6 (HMIPv6) to reduce handoff latency suffered by mobile nodes and signaling load incurred due to movement if nodes within the micro mobility region defined by HMIPv6. The HMIPv6 is considered as first widely accepted layered architecture for mobility management for IPv6 network. Influenced by the benefits of HMIPv6, many researchers have suggested extension of MIPv6 into multiple layers. However, there is very little work on finding optimal levels of hierarchy in such layered architecture. The focus of this paper is to evaluate the performance of a multilayer (N-layered with N as 5) MIPv6 architecture through experimental testbed. We have observed handoff latency, signaling overhead and tunneling cost and figured out the optimal levels of hierarchy that provides the best acceptable results for all the observed parameters. Since, HMIPv6 outperforms MIPv6 in terms of handoff latency and signaling cost, so we compare our results with HMIPv6. Testbed observation depicts that three levels of hierarchy in MIPv6 architecture provides optimal performance with 27% reduction in handoff latency and 67% reduction in signaling overhead compared to single layer architecture like Hierarchical MIPv6 (HMIPv6) protocol. Index Terms MIPv6; Testbed; Handoff Latency; Signaling Load; Tunneling Cost I. INTRODUCTION With the increased popularity of Internet and advancement in mobile handheld equipment, routing in mobile IP network has became an inevitable need. The mobile routing is the key technology that provides seamless mobility to subscribers roaming in a network. So far, there are many protocols proposed [1, 2, 3, 4] for providing seamless mobility in IP network. The efficiency of these mobility management protocols are primarily measured in terms of handoff latency, signaling cost and tunneling cost. Handoff latency is the time taken to reestablish the connection by a Mobile Node (MN) with its Correspondent Node (CN) during changeover of its point-of attachment [1] and least possible handoff latency is a desirable property. Minimized signaling overhead and tunneling cost are another two parameters that expected from mobility management protocols. Mobile IPv4 (MIPv4) [1, 2, 19] is the first protocol in this category of protocols. In the recent years, with the advancement of IPv6, Mobile IPv6 (MIPv6) [3] is gaining popularity for next generation wireless network. MIPv6 inherits some key features from parent IPv6 protocol such as large address space, optimized routing and security. However, it has few drawbacks which limit the use of MIPv6 in presence of highly mobile users. It treats both the local and global users in the same way [3]. So, it is not suitable for an environment where users frequently change their location within a local domain. To overcome this problem of MIPv6, it is extended to a new version called Hierarchical MIPv6 (HMIPv6) [4]. In HMIPv6 [4], a Mobile Anchor Point (MAP) is placed at the boundary of the local domain to restrict the movement of binding related messages within the local domain as long as MN stays within the same foreign network [3, 4, 5]. Observation reveals that HMIPv6 provides significant improvement in signaling load and handoff latency over MIPv6. Still, the protocol is not totally free of flaws. It does not perform well when nodes frequently change their subnets within the same foreign network. Because, the MAP needs to be updated every time it moves from one subnet to another. It is required even if the two subnets are adjacent. As the MAP is located long apart from the MN s actual location, a considerable signaling overhead is involved in such updates. Accordingly, due to long distance between MAP and MN, the handoff latency experienced by such MN is also large. The limitations of HMIPv6 is addressed in many alternative methods proposed in [7], [8], [1], [16], [17] etc. In all these proposals they have suggested to distribute anchor agents doi:1.434/jnw

2 JOURNAL OF NETWORKS, VOL. 9, NO. 7, JULY (like MAP in HMIPv6) into multiple layers. This layered concept is gaining noteworthy popularity in recent research. Stimulated by such works, the concept of multilayer hierarchical model for mobility management in IPv6 based network is discussed in many literatures. In the next paragraph few such literatures are briefly described. Wan et al. in [6] proposed a three layer hierarchical architecture for mobility management. The spotlight of this paper suggests a method of diminution in signaling overhead by allowing MN in the foreign network to register either with a higher or a lower layer agent or Home Agent (HA). A better signaling load is also demonstrated through simulation of the protocol. Works described in [7, 8] by Misra et al. propose a Three Layer Mobility Model (TLMM) based on MIPv4. This work is further extended to MIPv6 network in [9]. In TLMM the network is divided into backbone and local domain. Three anchor agents are placed in the local domain and a Global Mobility Agent (GMA) is placed at the boundary of the local domain and the backbone. However, no specific mobility pattern or session arrival pattern is considered for performance evaluation of these papers. Another similar hierarchical architecture for MIPv6 is found in [1]. A mathematical analysis to find optimal levels of hierarchy in a multi-level HMIPv6 network has been discussed here. Authors formulate the location update cost and the packet delivery cost in the multi-level HMIPv6. The numerical results projected in this paper depict various relationships among network size, optimal hierarchy, and signal to mobility ratio. However, the work has not provided explicit levels of hierarchy with optimal values of performance parameters. All the above stated research work shows that hierarchical organization of anchor agents perk up the signaling overhead and handoff latency. At the same time, the cost of packet delivered to MN located in foreign network increases linearly. Because, packets delivered to MN in the foreign network need to be tunneled by each of the anchor agent in the network hierarchy. An explanation of this packet tunneling cost is described in [7], [8], [9] and [1]. From the debate of packet tunneling cost in all these papers, it is tacit that, the number of layers in a hierarchical architecture cannot be increased after certain layers. Otherwise, despite of low handoff latency and signaling cost, degraded performance will be experienced due to extra computational overhead during packet delivery. The purpose of our paper is to examine the optimal number of layers in a multilayer hierarchical MIPv6 architecture through experimental test bed. Similar analysis through mathematical analysis is published in [19] and a preliminary version of the work presented in this paper is published in [13]. In this version, a detailed description of the test bed implementation process starting from architectural description of the layered MIPv6 model, its operational mode and message formats are provided along with the performance results. The work of this paper could further be extended to real life networks with large dimension. Rest of the paper is organized as follows. Section II describes the Hierarchical network architecture. Functionalities of hierarchical model are available in Section III. Section IV is the detailed description of the experimental testbed. Results are described in Section V with the conclusion in Section VI. II. HIERARCHICAL NETWORK ARCHITECTURE The proposed hierarchical network architecture is shown in Fig. 1. All functional entities are similar to those used in MIPv6 and HMIPv6. Only difference in our model is, we have n number of MAPs (used in HMIPv6) organized in hierarchical architecture. However, the operational model is noticeably different from both MIPv6 and HMIPv6. The functional entities and the operational model are discussed in the following subsections. A. Architectural Model The network architecture is divided into two sections: the Internet backbone and the Global domain (see Fig. 1). A global domain is a national network of a country and owned by a service provider (for example ERNET network in India). There are N-layers of MAP deployed in the global domain in a tree like architecture as recommended in [9] with a single MAP as root of the tree. The lowest layer of MAPs in the hierarchical tree is called layer 1 (L-1 MAP) and the top layer is called layer- N (L-N MAP). Access Routers (AR) are connected to the L-1 MAP. The MN in a network is served by AR. Every MAP in a specific layer except the top layer is connected to a MAP in its immediate higher layer. The top level MAPs of different global domain forms the backbone network in the proposed network architecture. We model the service area of an AR as hexagonal subnet (or cell) and each cell advertises dissimilar subnet addresses. The Home Agent (HA) of any visitor MN and the Correspondent Node (CN) with whom the MN communicates are connected to the backbone network either via a GMAP or directly. The term local domain indicates a region covered by single L-1 MAP. This local domain comprises of n-number of subnets served by an associated AR with each of these subnets. B. Operational Model The AR periodically broadcast Route Advertisement (AR) messages within its coverage area. The RA contains subnet prefix applicable for the subnet and n Care-of- Addresses (CoAs). These n CoAs represent n hierarchical MAPs in the layered architecture. When a visitor MN enters a foreign network, it waits for the RA message. On reception of the RA message, the visitor MN constructs its Link CoA (LCoA) from the subnet prefix contained in the RA message. It also acquires n-number of CoAs from the RA message for the layered MAPs in the architecture. The MN then sends Binding Update (BU) message to all the MAPs in order to register his location in the new network. It (the visitor MN) also sends the address of the top layer MAP (i.e. GMAP) to HA as its temporary location. All the MAPs as well as the HA confirms the registration of the MN by sending back a Binding

3 1684 JOURNAL OF NETWORKS, VOL. 9, NO. 7, JULY 214 Figure 1. Proposed network architecture Acknowledgement (BA) message. During the stay of the MN in that Foreign Network (FN) the packet will be tunneled to the GMAP s address. The GMAP then tunnels these packets to the lower layer MAP and finally to the AR under which the MN registers. The AR delivers packet to the MN directly. In a foreign network, the visitor MN generally moves to different subnets (also called cell). Every time it changes its subnet, it has to acquire a new LCoA and to get registered with the new AR and other higher layer MAPs. If the new cell is under a different L-1 MAP than its previous L-1 MAP, then the visitor node needs to exchange BU/BACK packets with next immediate higher level MAP, i.e. to L-2 MAP. The process can go on to the L-N MAP. The moment at which the visitor node crosses the L-N MAP, the HA of the visitor node and all the CNs that the MN communicates during handoff needs to be updated. The L-N MAP (Global MAP or GMAP) provides transparency of the visitor node s location to the HA and CN. As long as the visitor MN stays within the same foreign domain the HA and CN need not be updated because they contact the GMAP to communicate with visitor MN. C. Mobility Management Messages Three messages are used in the proposed architecture. They are Router Advertisement (RA), Binding Registration (or Binding Update (BU)) and Binding Acknowledgement (BACK) message. All these messages are carried over UDP and are designed with MIPv6 compatibility. However, few new fields are added to match the requirement of the hierarchical model. Each of these messages is described below. Router Advertisement (RA) message: The RA message format is shown in Fig. 2(a). An AR sends a unicast or broadcast message periodically. It allows a visitor node to discover default router in a foreign subnet. In addition, it also contains useful information about the CoAs required by the node to configure and register itself in the FN. The AR defined here can contain maximum of five CoAs so as to enable five levels of hierarchy in the architecture. Description of various fields of RA message follows: The type field of RA message specifies the type of the data carried out in Internet Control Message Protocol (ICMP) packet. This value is set to 134 as in MIPv6 notation. The current hop limit field specifies the number of hops that the message should traverse. This field is set in such a way that it traverses only to the nearby host on the link. The M field indicates that the host should use stateless configuration if set to and stateful configuration if set to 1. The O field is used in combination with M field to use stateful configuration. The H field if set to 1 indicates that the router advertising itself as a Home Agent. The router lifetime field specifies the period that the router can be used as a default router. This field is set to to indicate default router always. The router reachable lifetime is used to declare the reachability of the router from the nearby hosts in seconds. The retransmission timer specifies the frequency of address resolution to be done by host in milliseconds. In MIPv6 the care-of address is transmitted as prefix information to the option header extension. In

4 JOURNAL OF NETWORKS, VOL. 9, NO. 7, JULY hierarchical implementation CoAs are included in the RA as separate field. There are five such CoA fields of 128 bits and one LCoA field. (a) (b) Figure 2. (a) RA message format, (b) Binding registration/bu message format Binding Update (BU) message: When an MN is away from its home, it binds its temporary address with the HA using Binding Update (BU) message. The BU message format is shown in Fig. 2(b). The mobility header defined in MIPv6 as an extension of IPv6 header is used in this hierarchical model to carry BU information. The payload proto, header length, mobility header type and checksum fields are fixed and remain in all the messages. The Payload type is set to 59 to make it compatible with MIPv6 binding update message and indicates that mobility header is the last header [6]. The Header length specifies the length of the header excluding first eight octets. The Mobility header type (MH type) represents the type of message included in the header. For binding update message, the value of this field is 5. The next five bits are called layer count flag and signifies the total number of layers supported by the architecture. An entry of 1 in the flag bit position means the presence of that layer. For example, if the entry of the five flags is then it indicates that five layers are implemented. The checksum is calculated for the entire extension header and is included in message for error detection. The 16 bits sequence number field uniquely identifies each BU message and ensures ordered acknowledgement. The A flag is used to demand an acknowledgement; H flag indicates that the binding update message is sent to home agent. The lifetime field specifies the duration of binding in the binding cache. The value in this field indicates the removal of the entry from the cache. The home address field includes the permanent address of the visitor MN. The top level CoA field carries the address to which the receiver of the BU message should send the reply. This address is considered as the temporary address of the mobile node within a foreign network. Binding Acknowledgement (BACK) message format: On successful reception of BU message, HA and other MAPs in the hierarchy need to acknowledge the MN about the binding of the CoA in its database. In the implementation of hierarchical mobile architecture, Binding Acknowledgement (BACK) is used to perform this task. The format is same as the BU message. The value of mobility header field is assigned to 6 to indicate acknowledgement. Although the number of fields are less in binding acknowledgement message, it is padded with zeros to make the size same with BU message. III. FUNCTIONALITIES ASSIGNED TO DIFFERENT ENTITIES IN THE HIERARCHICAL MODEL Every element in the architecture is assigned a set of responsibilities as described in following subsections. A. Functions of MN in a Foreign Network Algorithm 1: Functions of MN in Foreign Network (Binding update process) Step 1: MN constructs the new LCoA from the information contained in the RA message. Step 2: Determines the number of layers implemented in the hierarchical model from the layer count flag (see RA message format). Step 3: Determines the number of layers to be updated by observing the CoAs in the message. Step 4: Send BU message to all anchor agents including the first unchanged CoA contained in the advertisement. Step 5: If all CoAs are different then BU is sent to HA and CNs. At the time of residing in the home network, an MN acts as an ordinary node in the network and it receives packets using normal IPv6 routing mechanism. If the MN visits a foreign network, then the special functions for handling mobility are activated. When it enters a foreign network, or changes its subnet in a foreign network, the MN constructs its LCoA and other necessary CoAs from the RA message of that subnet register itself with AR and various MAPs. After successful registration with the AR and hierarchical MAPs, the MN informs its current location to the HA so that the HA can redirect data to MN s new location. Otherwise, all the packets destined to MN will be lost as it is not in its permanent location. The subnet prefix in the RA message determines the movement of an MN to a new area. When a visitor node detects a new subnet, it executes Algorithm 1. The binding update is very crucial function of any mobility management architecture. A careful implementation of this process may greatly improve the performance of the architecture. Every element of the network should be designed to act promptly on the update process with top most priority. A. Functions of HA HA keeps track of all mobile nodes that are visiting some foreign network. It maintains a database of all MN that wants to receive packets when they are away from home. This database contains MN s permanent address, current CoA, and lifetime of the association. The HA performs two operations: processes the binding update message received from the MN and tunnels the packets to the current location of the node.

5 1686 JOURNAL OF NETWORKS, VOL. 9, NO. 7, JULY 214 On receipt of the binding update message the HA performs Algorithm 2 as follows: Algorithm 2: BU processing by HA Step 1: It searches the database for the existence of the MN s permanent address and the corresponding CoA. If one such entry is found then the entry is updated else a new entry is created with the MN s permanent address, current CoA and binding lifetime. Step 2: HA prepares a BACK message and sends it to MN s CoA On reception of data packets from the CN by the HA it performs following steps: Algorithm 3: Data processing by HA Step 1: HA searches the database for existing CoA of the destination mobile host. Step 2: The packet is tunneled within an IP packet and sends to the CoA of the destination. Step 3: HA constructs a packet stating the current address of the MN and sends to CN. The format of binding update packet is used by the HA to send the location information to the CN. C. Functions of CN All CNs that communicates with an MN located in a foreign network maintains a list of MN s current location. When there is a packet to send, CN executes algorithm 4. Algorithm 4: Functions of CN to send data to MN Step 1: It searches the database to find the CoA of the MN that it wants to communicate. Step 2: If entry found it tunnels the packet to the CoA of the MN. Otherwise, it sends the packet to the default router of the MN. MN sends BU message to the CN during handover. On receipt of such messages, CN performs following steps. Algorithm 5: BU message processing by CN Step 1: CN searches the database for the existence of the MN s permanent address and the corresponding CoA. The database is updated if entry is found else creates a new entry. The entry contains the MN s permanent address, current CoA and binding lifetime. Step 2: CN prepares a BACK message and sends it to MN s CoA. D. Function of AR AR broadcasts RA message periodically within the subnet of its coverage. On receipt of the advertisement, the MN constructs the LCoA and sends it to AR for Duplicate Address Detection (DAD) [14, 15]. When router receives a DAD request it performs the following steps of Algorithm 6: Algorithm 6: DAD process in AR Step 1: It verifies the CoA constructed by the MN and accepts if the address is not previously assigned to any other MN. Step 2: AR enters the information of the MN s permanent address, CoA and lifetime in the database. E. Functions of MAP All anchor agents maintain a list of visitor MNs under their coverage. MAPs are configured to process binding related messages and tunnel packets to the lower layer anchor agent towards the path to the MN. To process binding messages, a MAP performs the following steps: Algorithm 7: BU processing by MAP Step 1: It updates the database with the location information of the MN. Step 2: Anchor agent prepares a BACK message and sends it to MN. When anchor agent receives a tunneled packet it performs the following steps: Algorithm 8: Packet Tunneling by MAP Step 1: Anchor agent searches the database for existing CoA of the destination MN. Step 2: The packet is tunneled within an IP packet to the CoA of the destination. All the above stated algorithms are implemented using C language in Linux environment. The experimental test bed is designed to observe the hierarchical architecture in the laboratory environment. Complete description of the test bed is given in the next section. IV. TEST BED IMPLEMENTATION The proposed hierarchical architecture of Fig. 1 is implemented with five layers. The block diagram of the test bed is shown in Fig. 3. The test bed is configured in the departmental laboratory with different subnets as shown in the diagram. The implementation details are discussed in the following subsections. A. Description of Test Bed Architecture: The sub network N 1 is the home of an MN (say M 1 ) with H 1 as its HA. The subnet N 1 is connected to the Internet through gateway G 1. It belongs to both Internet backbone and internal network. During the observation, M 1 is moved to network N 3 under the coverage of access point A 1. Three access points A 1, A 2 and A 3 are located in network N 3 and connected via access router R 1, R 2 and R 3 respectively. Dynamic Host Configuration Protocol (DHCPv6) is configured in all APs. Initially, MN (M 1 ) acquires its LCoA from these APs. To perform DAD, MN sends the acquired address to AR. The router R 1 maintains a database of all visitor MNs under the coverage of A 1, A 2, and A 3. The CN (C 1 ) is located in the network N 2 connected via the gateway G 3. There are five MAPs L 1, L 2, L 3, L 4, and L 5 configured in the test bed. Two routers are placed as intermediate routers between every two successive anchor points in the diagram. The test bed comprises of four HP Z4 workstations and two IBM Xeon Servers (total six) configured as anchor agents and HA. Ten layer-3 switches are distributed uniformly as intermediate routers. Distance between two intermediate routers or between a router and an anchor agent is considered as one hop. The top level MAP (marked as L 5 MAP) is connected to the institution s main network through optical fiber media. The CN is a PC which is connected to the Internet Service Provider s (Reliance) network. HP 673S Laptops are configured as MN and allowed to communicate with HA and CN through different anchor agents from the AP under L 1 MAP. To implement hierarchical protocol stated in this paper, a set of UNIX socket programs are written and deployed in all MAPs, MN, HA and CNs. The functionalities stated in section III are deployed in all nodes of the hierarchical model. The MN maintains the address of it s HA in its

6 JOURNAL OF NETWORKS, VOL. 9, NO. 7, JULY Figure 3. Test bed diagram database all the time. DAD is performed in the access router as writing program to implement DAD in access point is complicated. Once the DAD is over, the visitor MN can perform BR/BU. When MN detects the change in the subnet, it performs binding update. To record the results for single layer, Layer-5 MAP is placed in the border of the local domain. Then the second anchor agent is added at an equal distance between the MN (or wireless AP) and L-5 MAP. Again, to add the third layer, the new anchor agent is placed in such a way that the distance from the AP to L-1, L-1 to L-2 and L-2 to L-5 MAP are equal in terms of hop count. Similarly, any new layer is added with the re-arrangement of anchor agents to make the distance to be uniform among them. B. Implementation of MIPv6 and HMIPv6 Although the test bed is designed for multi layer architecture it can also be used for both MIPv6 and HMIPv6 architecture. To use the test bed as MIPv6 model, anchor agents (L 1 to L 5 ) are replaced with layer 3 switch. The HA, CN and movement of MN is carried out in the same way as described in subsection (subsection

7 Handoff Latency (ms) Handoff Latency (ms) 1688 JOURNAL OF NETWORKS, VOL. 9, NO. 7, JULY 214 IV.A above). The MN sends the BU message to the HA for every new LCoA it acquires in a new subnet. To test the parameters of HMIPv6, only L-5 MAP is kept at the boundary of the local domain to handle micro mobility of nodes and all other MAPs are replaced by ordinary routers. The initial registration of MN during its visit to a foreign network is done with the HA. For rest of the new LCoA acquired by the MN is communicated to the MAP through BU messages. Functionalities of other components will remain same as described earlier. A. Handoff Latency V. TEST BED RESULTS To calculate handoff latency, the mobile nodes (As M 1 in Fig. 3) are moved to the coverage of A 1 in the subnet N 3. Then these MNs are allowed to change locations within the coverage of A 1, A 2 and A 3. The experiment is conducted for 2 minutes. The time taken to receive the last packet under old AP and the first packet in the new AP is recorded and is considered as handoff latency including the time needed to acquire LCoA from the AP under which MN is resided MIPv6 2-Layer 4-Layer Number of users (a) Local Update Global Update (b) HMIPv6 3-Layer 5-Layer Number of layers Figure 4. (a) Handoff latency Vs user; (b) Handoff latency Vs layers In Fig. 4(a) handoff latency is shown for all the protocols against number of users. The latency is highest for MIPv6 and lowest for five layer architecture. In MIPv6 the every location change need to register with the HA, so handoff latency is more. As soon as we add intermediate anchor agents handoff latency reduces as the registration is done with the local agent rather than the HA. It is also observed that latency increases with the increase in number of MNs. Since, in presence of large number of MNs, acquiring LCoA takes longer time, so handoff latency increases. It is further noticed that a reduction of around 2% in handoff latency can be achieved for two layer architecture compared to HMIPv6. When layer-3 is added handoff latency reduces by 7% and for the next 2-layers this reduction comes down to 3% and.4% respectively compared to HMIPv6 architecture. Addition of a new layer increases system complexity but no significant improvement in handoff latency is observed. So, three layers of hierarchy may be considered as optimized for handoff latency. In Fig. 4(b) handoff latency suffered by nodes performing local and global handoff is shown. To compute global handoff, MNs are allowed to move outside the local domain. The results are taken with 25 MNs and allowing 15% MNs to perform global handoff. The local handoff decreases with the increase in number of layers. However, reduction is large upto three layers and beyond layer three no significant improvement in found. On the contrary, global handoff latency is not affected by the presence of layers. It is because the HA and CNs must be updated for every global handoff. B. Signaling Load Signaling load (or cost) is computed by measuring the number of bits injected per second into the network during the period of handover. The injected bits are due to the binding management packets exchanged by MN with corresponding agent (any intermediate MAP). This cost is influenced by the size of the BU/BACK message (118 bytes) and the distance traversed by the message (number of hops). Higher the number of hops, more the signaling cost. Fig. 5 (a) is the signaling load against varying number of users. For MIPv6, signaling load is more than all other protocols. With the increase in the number of MNs, the load also increases. It is observed that the signaling cost decreases with the increase of layers. However, the reduction is not uniform for al layers. For a layered architecture of two, the signaling load shrinks around 37% compared to HMIPv6 (or one layer architecture). For addition of layer 3 it is reduced further by 3% (total 67% compared to single layer). However, for fourth and fifth layer the reduction of % signaling cost are only 2% and 2.5% respectively. Hence, it may again be stated that the drop in signaling cost is effective upto layer three. In the Fig. 5 (b) the signaling load for local and global update with respect to number of layers are depicted. It is noticed that signaling load for local update decreases sharply upto layer three. The signaling load changes only due to varying distance traversed by BU/BACK messages. More the layers in the network, less the distance traversed by the mobility related messages and hence lower the signaling cost. But after layer three, when fourth and fifth layer is added re-arrangement of anchor agents reduces the distance to be traversed by BU/BACK message with small amount in terms of hop count. So, the reduction in signaling load is around 2-2.5%.

8 Delay Bandwidth product (kbps) Delay Bandwidth product (kbps) Cost per byte (in ms) Signaling load (Kb) Total tunneling cost (ms) Signaling load (Kb) JOURNAL OF NETWORKS, VOL. 9, NO. 7, JULY MIPv6 HMIPv6 2-Layer 3-Layer 4-Layer 5-Layer Number of users (a) (b) Figure 5. (a) Signaling load Vs user; (b) Signaling load Vs layers (a) (b) Figure 6. (a) Delay Bandwidth product Vs users; (b) Delay Bandwidth product Vs layers C. Delay Bandwidth Product Local Update Global Update Number of layers MIPv6 2-Layer 4-Layer HMIPv6 3-Layer 5-Layer Number of users Local Update Global Update Number of layers Delay-bandwidth product is another important parameter to measure the performance of any TCP/IP based network. A lower delay-bandwidth product is always a desirable property for a packet switched network. Fig. 6(a) and 6(b) represents the delaybandwidth product for the test bed result. It is observed that this product decreases with the increase in number of layers. A reduction of 53% for two layers, 18% for three layers and 5% both for four and five layers are noticed compared to single layer. The product for local and global update is also shown separately. Considering the importance of delay bandwidth product in TCP/IP network, three-layer may be considered as favorable one. C. Tunneling Cost Sesion size (number of packets) PS = 25 PS = 5 PS = 1 (a) Layers (b) Figure 7. (a) Total tunneling cost Vs session size; (b) Per-byte tunneling cost Vs layers Tunneling cost is measured in terms of encapsulation and de-capsulation time in ms. Fig. 7. (a) shows the encapsulation decapsulation cost for varying session size. The size of the packet is 5 bytes. The tunneling cost increases with increase of layers. Also, larger the session size more the tunneling cost. The tunneling cost per byte is also calculated in the context of the test bed design. Fig. 7.(b) represents per byte encapsulation and decapsulation cost for the hierarchical architecture with different packet size. The per-byte cost decreases with the increased size of the packet. So, a layered architecture can be designed to reduce per byte tunneling cost with large packet size. VI. MIPv6 HMIPv6 2-Layer 3-Layer 4-Layer 5-Layer CONCLUSION Test bed implementation process of multilayered mobility management architecture based on MIPv6 protocol has been discussed in this paper. The 5-layered hierarchical test bed model is implemented in the departmental laboratory. Several experiments have been carried out for the measurement of the performance parameters such as handoff latency, signaling overhead

9 169 JOURNAL OF NETWORKS, VOL. 9, NO. 7, JULY 214 and packet tunneling cost. Observations reveal that three levels of hierarchy in MIPv6 architecture provide optimal performance in terms of the above mentioned parameters. We noticed a 27% reduction in handoff latency and 67% reduction in signaling overhead for a three layer architecture as compared to single layer (HMIPv6). It is also seen that although the packet tunneling cost increases with the increase in layers, per byte tunneling cost could be reduced by increasing the size of the packets to its maximum size supported by the underlying network. The model described in this paper is suitable for extension of layered hierarchical architecture in wireless environment in large scale. ACKNOWLEDGMENT This work is supported by All India Council for Technical Education (AICTE), New Delhi, India, under Research Promotion Scheme(RPS) F.No.: 832/BOR/RID/RPS-29(NER)/ for the Financial Year REFERENCES [1] C. Perkins, RFC 3344 IP Mobility Support for IPv4, August 22. [2] C. Perkins, IP Mobility Support for IPv4 (revised), IETF draft-ietf-mip4-rfc3344bis-1, April, 21. [3] Johnson and C. Perkins, Mobility support in IPv6, IETF draft, draftietf-mobileip-ipv6-15.txt, July 21 [4] H. Soliman, C. Castelluccia, K. El-Malki, L. Bellier, Hierarchical MIPv6 Mobility Management (HMIPv6), RFC 414 August 25. [5] Debashis Saha, Amitava Mukherjee, Iti Saha Misra and Mohuya Chakraborty, Mobility Support in IP: A Survey of Related Protocols, IEEE Network, vol. 18(6), pp.34-4, November/December 24. [6] Wan Zheng et al., A three level mobility management scheme for hierarchical mobile IPv6 networks, Journal of Zhejiang University Science A, vol. 7(12) pp , 26. [7] M Chakraborty, I.S. Misra, D. Saha and A. Saha, TLMM- MIP based Three Level Mobility Model, Elsevier Computer Communication- vol. 3, pp , 26. [8] Iti S. Misra et al., An approach for Optimal Hierarchical Mobility Management Network Architecture, IEEE 63 rd VTC vol. 1(1), pp , Sep 26. [9] Iti Saha Misra and D. Saha, Hierarchical Mobility Management, Architecture for MIPv6 based Wireless Data Networks, Journal of Computing and Informatics Issue, pp. 2-9, Nov. 26. [1] Sangheon Pack, et.al, A Study On Optimal Hierarchy in Multi-Level Hierarchical Mobile IPv6 Networks, Proc. of IEEE Globecom 4, vol. 2, pp , 24. [11] S. Das, A. Misra, P. Agrawal, and S.K. Das, TeleMIP: Telecommunications-Enhanced MIPv4 Architecture for fast Intradomain Mobility, IEEE Personal Communications, pp. 5-58, Aug 2. [12] Nitul Dutta and Iti Saha Misra, Cost Analysis of a Three Layered MIPv6 (TLMIPv6) Mobility Model and HMIPv6, Int. Journal on Computer Science and Engineering, ISSN: , Vol. 2S(1), pp , January 21. [13] N.Dutta and I.S.Misra, Test Bed implementation of N- Layered Mobile IPv6 Based Network Architecture in Search of Optimal Performance, IEEE Globecom Workshop on Heterogeneous, Multi-hop Wireless and Mobile Networks Miami, USA, Dec 21. [14] N. Moore, Optimistic Duplicate Address Detection (DAD) for IPv6, RFC 4429, April 26. [15] Deng Ya-ping and Wu Ying-qiu, Research on HMIPv6 Handover Latency of Improved DAD policy, Journal of Computer Engineering and Applications, vol. 46 (3), pp , 21. [16] REN San-yang, CHAI Rong etc, Proxy Mobile IPv6 Based Inter-domain Mobility Management Approach and Performance Analysis, Application Research of Computers, vol. 27(3), pp , 21. [17] Yvette E. Gelogo, Ronnie D. Caytiles and Byungjoo Park, A Robust Secured Mobile IPv6 Mechanism for Multimedia Convergence Services, International Journal of Multimedia and Ubiquitous Engineering, Vol. 6 (4), pp , Oct [18] Tran Cong Hung and Nguyen Thi Thuy, Research Handover on Mobile IP, Cyber Journals: Multidisciplinary Journals in Science and Technology, Journal of Selected Areas in Telecommunications (JSAT), pp , July 212. [19] Nitul Dutta and Iti Saha Misra, Mathematical modelling of Hierarchical Mobile IPv6 Based Network Architecture in search of an optimal Performance, Proc. of IEEE sponsored 15th Int. Conf. on Advanced Computing and Communications (ADCOM 7), Guwahati, India, pp , Dec 27. Dr. Nitul Dutta is currently Associate Professor in the Department of Computer Science and Engineering, Sikkim Manipal Institute of Technology, Sikkim. He received his B.E. degree in Computer Science and Engineering from Jorhat Engineering College, Assam (1995) and M.Tech in Information Technology from Tezpur University Assam (22). He completed his Ph.D. in engineering in the field of Mobile IPv6 at Jadavpur University (212). He has published more than twenty research papers in different International Journals, referred International and National Conferences of repute. His current research interests are in the areas of mobility management architecture and protocols in IPv6 based network and Cognitive Radio network. Dr. Iti Saha Misra is currently Professor in the Department of Electronics and Telecommunication Engineering, Jadavpur University. She received her B.Tech. degree in Radio Physics and Electronics from Calcutta University (1989) and her Master s in Telecommunication Engineering from Jadavpur University (1991). She completed her Ph.D. in engineering in the field of microstrip antennas at Jadavpur University (1996). She is the recipient of the prestigious Career Award for Young Teachers from the All India Council for Technical Education (AICTE) in the financial year and obtained the IETE Gowri memorial award for being the best paper in the general topic of 4G networks: Migration to the Future. She is the Senior Member of IEEE, founder Chair of the Women In Engineering, Affinity Group, IEEE Calcutta Section. She has published more than hundred

10 JOURNAL OF NETWORKS, VOL. 9, NO. 7, JULY research papers in different International Journals, referred International and National Conferences of repute. Her current research interests are in the areas of mobility management network architecture and protocols, integration architecture of WLAN, WiMAX and 3G networks. Her other research activities are related to microstrip antennas and design optimization of wire antennas using numerical techniques. Mr. Kushal Pokhrel is currently Associate Professor in the Department of Electronics and Communication Engineering, Sikkim Manipal Institute of Technology. He received his B.E. degree in Electronics and Telecommunication Engineering from Mumbai University (23) and M.Tech in Digital Electronics and Advanced Communication from Sikkim Manipal University (25). He is pursuing his PhD in Engineering at Sikkim Manipal University. His current research interests are in the areas of IPv6 and mobility management protocols. Mission simulation and Quality & Reliability Analysis of ISRO Launch vehicles and Satellite systems and during 1995 to 26 at Regional Remote Sensing Service Centre, ISRO, IIT Campus, Kharagpur in the areas of RS & GIS techniques for the natural resources management. His areas of research interest are Data Mining, Simulation & Modeling, Network, Sensor Network, Information Security, Optimization & Genetic Algorithm, Digital Image processing, Remote Sensing & GIS and Software Engineering. Dr. Ghose chaired a number of international/national conference sessions. He has conducted quite a number of Seminars, Workshop and Training programmes in the above areas and published 126 technical papers in various national and international journals in addition to presentation/ publication in several international/ national conferences. Till date, he has produced 8 Ph.Ds and research assistance given for 2 Ph.Ds. Presently 8 scholars are pursuing Ph.D work under his guidance. Dr. Ghose is having 8 sponsored projects worth of 1 crore. Dr Ghose also served as technical consultant to various reputed organizations like IIT, Chennai, IIT Kharagpur, WRI, Tricy, SCIMST, KELTRON, HLL, Trivandrum. He can be reached at headcse.smit@gmail.com Dr. M. K. Ghose is currently Professor and Head of the Department of Computer Science & Engineering at Sikkim Manipal Institute of Technology, Sikkim, India. Prior to this, he worked in the internationally reputed R & D organization ISRO during 1981 to 1994 at Vikram Sarabhai Space Centre, ISRO, Trivandrum in the areas of